In recent years, a device, called a home gateway device or a gateway device (referred to as a “GW” hereinafter), is known that connects a home network in a house such as a residence, a building, etc. and an external network such as the Internet etc. (for example Japanese Laid-open Patent Publication No. 2010-245681 and Japanese National Publication of International Patent Application No. 2001-526814).
For example, a service that uses application software operating in a server or a gateway device in the Internet conducts, through a GW, data collection or control on a management target device such as a sensor, a home appliance, etc. connected to the home network. More specifically, in an example of the service, a home appliance in a house is controlled from outside of the house via the Internet. In another example of the service, an electric power company or a gas company remotely reads the usage meter in each contracted house.
When a plurality of services of this type are used in one home network, there can be a case where a plurality of GWs are connected to one home network and data collection is conducted on one management target device by the plurality of GWs.
Note that a technique is known that uses an automatic cache method, a transparent cache method and a distributed cache method provided along the path from a client to the home server in a network (for example WO2006/126355).
When data collection is conducted on one management target device by a plurality of GWs, there is a possibility that a plurality of data obtain messages are transmitted to one management target device from the plurality of GWs in a short period of time. Since there can be various types of management target devices, some management target devices may have insufficient hardware resources such as reception buffers etc. In such a case, there is a possibility that when for example a plurality of data obtain messages concentrate in one management target device and a number of packets exceeding the number that can be stored by the reception buffer have been received, an overflow occurs in the reception buffer and the packets are discarded, which affects the services.
As a countermeasure against an overflow in a reception buffer, a method size of the reception buffer may be increased so as to store more number of messages. However, it is difficult in practice to realize this method because home network systems usually use existing home appliances or sensor devices, making it impossible to modify the hardware.